212 Captiva BR 5.7 Range?

HD2Pct

Hi gang-

Just like 95% of us I am a bit land-locked. I'm here in NE Illinois but on occasion I want to drag the ship onto Lake Michigan in the greater Chicago area. There aren't a lot of gas stops in that neck of the woods. Based on Merc specs, I would consume 21 GPH at WOT, and their specs seem to totally dismiss boat loading. That means basically and maybe at best, a 2-hour range with a 42-gal tank with calm seas (let's at least 50 mph with this boat) and of course I would NEVER get to do that speed on Lake MI under normal condx. I mean, when is it glass smooth?

I am a newbie and could really benefit from your comments here. What are people getting out of their boats in terms of miles range and under what power settings and conditions?

TIA

howardrams

I've had 2 boats with the 5.7 and the most economical cruise is about 25-30 mph, just up on plane, which is approx 3500-4000 rpm.  At that speed you should get about 2 mpg and consume roughly 10 gallons per hour under good lake conditions (waves 2 feet or less).  It was with my old 5000 pound boat and has been about the same with my new 7000 pound boat.  My true results matched pretty well with the published test results for my boats from Boating magazine. I generally never run wide open which really kills fuel mileage.

212rowboat

EFI or carb?  what prop style/material/pitch?  

I run a 212 BR with a slightly bumped SBC... started life as a 305, now a 314 and has a healthy cam and worked heads... it turns a 19p ron hill marine pleasure five in stainless... picks up plane around 2400RPM and holds it around 22mph/2200RPMish... best cruise I can extrapolate is around 3400RPM and somewhere around 35~38MPH, and according to vacuum gauge.  I'm thinking the range to fuel ratio drops after that pretty solid... it'll top @5200RPM and right at 60mph, now that i have it timed right (that prop has ridiculous grip)... though that's near twice the cruise speed, it's SUCKING DOWN the fumes at that rate, and that is according to my fuel gauge..... 

it's all about the prop, sir...

you can go either way depending on your applied torque- some choose to turn max RPM in the lower range of 4400RPM to 4600RPM, and turn a further bite prop- while others use their discipline and sensibilities to control RPM's, and allow the engine to easily turn higher RPM's... I prefer a steeper prop (lower pitch) and less lug on the engine... my engine will turn faster than a OE merc w/o issues- OE merc users should stay under the 4800rpm limit on older engines and 5200 on the newer... 

with the 42gal tank, and with the prop/torque band/best cruise speed according to vacuum gauge, I'm thinking I can get somewhere around 2~2.5MPG... or, around 70miles before I'm looking hard for a fuel point.. I ain't gonna cut that but so close... 

HD2Pct

Very good guys. That is great input.

Thanks!